Some of sensor modules of pressure sensors include a diaphragm, on which four resistor elements each configured to detect a strain, resistor element electrodes connected to the resistor elements and a linear conductor are formed. The linear conductors each serve as a connector for the resistor element electrodes, terminal(s) and the like and each have a predetermined wiring pattern.
A typical example of the sensor module includes a diaphragm, on which a plurality of linear conductors and resistor element electrodes are formed using screen printing. A resistor element is formed between adjacent ones of the resistor element electrodes using screen printing (Patent Literature 1; Japanese Patent No. 3691842).
In Patent Literature 1, the resistor element electrodes are thinly formed to face each other and the resistor element is formed in a rectangle in a plan view so that the resistor element covers the resistor element electrodes at both sides thereof.
A typical example of a dynamic quantity sensor configured to detect dynamic quantity includes: a metal substrate configured to receive the dynamic quantity; a multilayered insulation layer covering a surface of the metal substrate; a rectangular strain-resistance element printed and burned on the surface of the multilayered insulation layer; and a linear conductor printed and burned so as to be connected with the strain-resistance element (Patent Literature 2; JP-A-9-243472).
A typical example of a printed resistor, which is applicable to an electronic circuit unit, includes a pair of mutually parallel belt-shaped linear conductor patterns on one side of an insulation board, and a resistor provided between the linear conductor patterns (Patent Literature 3; JP-A-2004-55946).
In the typical example disclosed in Patent Literature 1, the resistor element, resistor element electrodes, and linear conductors are formed by the screen printing, in which a conductive paste is pushed out through an opening of a screen using a squeegee. Specifically, in order to form a pair of resistor element electrodes, the conductive paste is thinly pasted on the diaphragm. In order to form the resistor element, the conductive paste is pasted between the pair of resistor element electrodes in a form of a rectangle in a plan view. Usually, in order to reduce the amount of the conductive material to be pasted, the conductive paste is pasted so that a peripheral end of the resistor element electrode aligns with an end of the resistor element.
However, since the paste has fluidity, when the conductive paste is linearly pasted on the diaphragm using the screen printing, the shape of the paste is slightly rounded at the start of the pasting (i.e. the peripheral portion). When a part of the resistor element electrode formed by the screen printing is rounded and the resistor element is overlapped with the rounded part, the distance (i.e. resistance) of the resistor element varies along a longitudinal direction of the resistor element electrode. Though it is necessary to adjust the resistances of the four resistor elements to a predetermined value, when the connection statuses between the resistor elements and the resistor element electrodes respectively differ, each of the resistor element exhibits different resistance. When the resistances differ as described above, the offset value of the sensor becomes uneven, thereby requiring troublesome output adjustment in use.
In the typical example disclosed in Patent Literature 2, since the width of the strain-resistance element is set large with respect to the width of the linear conductor, even when the strain-resistance element is misaligned during the printing process, variation in temperature characteristics of the strain-resistance element can be restrained. However, the typical example disclosed in Patent Literature 2 does not, as in the typical example of Patent Literature 1, provide any solution for the above problem associated with the start of the printing of the linear conductor.
The typical example disclosed in Patent Literature 3 is applied to an electronic circuit unit and is not used for pressure measurement. In addition, only a set of a pair of conductive patterns and a resistor is disclosed, where nothing is suggested on the problem associated with the difference in the resistances of the four resistor elements defining a bridge circuit.